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November 30, 2006

The Homogenization and Reporting of Groundbased Atmospheric Datasets for the

Validation of Earth Observing Satellite Instruments - the Aura and Envisat validation

approach using HDF

B. R. Bojkov, NASA-GSFC (USA)

R. M. Koopman, ESA-ESRIN (I)

M. De Maziere, BIRA-IASB (B)

I. Boyd, NIWA (NZ)

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November 30, 2006

Outline

• Context (and some history)

• Implementation for Envisat and Aura

• Future activities

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November 30, 2006

• Why did we do this for atmospheric sciences?

(from the perspective of validation)

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November 30, 2006

• Ensuing from European Arctic campaigns in the 1990’s

• ~35 stations reporting» operational NRT and scientific

• All stations uses NASA-Ames» “simple” ASCII

• More than 18 file variations» nomenclature and formulations

• Clear need of homogenization

Near-real-time ozonesondes

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November 30, 2006

The problem is accentuated:

• Different measurement networks» LIDAR, MWR, FTIRs, UV-Vis instruments, etc.

• Different platforms» Groundbased, aircraft, balloon, ship, in-situ, etc.

• Different agencies» “Dialog” across timezones, reporting facilities, etc.

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November 30, 2006

So, in 1996/1997…

• Near impossible to use effectively for research or tools/RDB/web implementations

• Need to resolve this “file reporting ” problem by investigating/understanding the state of affairs in the field

• First objective: satellite validation of atmospheric chemistry instruments» up and coming ESA and NASA missions

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November 30, 2006

COSE

• COSE - Compilation of atmospheric Observations in support. of Satellite measurements over Europe

• European Commission (EC) funded project

• Consortium of 25 groundbased and satellite teams

• Timeline: 1998-2000

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November 30, 2006

COSE (2)

• Approach:» Investigated existing file formats, usage, community needs

in consultation with the different stake-holders

• Recommendations:» Defined fixed file formulation: HDF4 (SDS)» Rigid metadata, including strict guidelines for attributes

requirements, variable naming, etc.» Make files truly homogeneous and self explanatory» Final document by Bojkov et al., 2002 (available through

AVDC)

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November 30, 2006

Basic HDF4 SDS file layout

• Global attributes: 31 attributes» Data source / contact information» Dataset contents / location / …» File generation date / version / caveats / …

• Attributes for each SDS: 19 attributes» Variable description / notes / caveats» Dependencies / dimensions» Units / SI conversion factor / Valid min. & max. / Fill values» Display attributes (label, axis, …)

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November 30, 2006

Global attributes

Variable attributes

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November 30, 2006

Variable naming convention

• Variable name construction: 3 part construction

VARIABLE_NAME + VARIABLE_MODE (+ VARIABLE_DESCRIPTOR)

• Example: » The variable name for O3 measured by an O3sonde and a Brewer spectrometer are:

O3_CONCENTRATION for the ozonesondeO3_VERTICAL.SOLAR for the Brewer in direct sun modeO3_VERTICAL.ZENITH for the Brewer in Umkehr mode

» The RMS for a FTIR ozone measurement can be expressed as:

O3_VERTICAL.ZENITH_UNCERTAINTY.RMS

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November 30, 2006

Similar conventions for

• Attribute entries

• Instrument naming

• File names

• …

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November 30, 2006

First Implementation: ESA

• Spring 2000: ESA Envisat mission was is it’s final validation planning:» 10 instruments, focus on land, atmosphere and oceans.

• ESA required:» Fully relational database for calibration and validation» File “QA/QC” on all incoming files» Specifically COSE concept, including HDF 4, to be

implemented for atmosphere and ocean instrument validation

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November 30, 2006

Envisat Cal/Val

• Implemented in October 2000» Meets all ESA requirements, including QA and the RDB» 200+ users, intercontinental participation» Backbone of the coordinated validation efforts of 3

atmospheric and 2 ocean instruments» Data sources collected from ship-based to satellites» Extended to other Envisat/ESA validation activities (2004)

• One issue: heterogeneous reporting- the ozonesonde problem was back!

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November 30, 2006

2004-present

• EOS-Aura validation activities

• The Network for Detection of Atmospheric Composition Change (NDACC - former NDSC)

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November 30, 2006

Aura Validation Data Center

• Support the NASA EOS-Aura mission» 4 atmospheric instruments» troposphere to mesosphere measurements» Share validation communities with Envisat

• AVDC uses the same concept/approach as Envisat» Maintain Envisat files compatibility

• Operational since October 2004» ~300 users - many new participants» ~2TB validation data

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November 30, 2006

AVDC modifications

• Refined file and metadata requirements through thorough analysis of Envisat Cal/Val in early 2004» Eliminate common user errors and misconceptions» Added HDF5 implementation (user request due to HDF5 satellite

data)

• Implemented rigid measurement reporting templates» Collaborative effort with NDACC» Measurement specific and defined by expert community» Results in truly homogeneous files

• Document describing changes by Bojkov et al., 2006 available through AVDC web site

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November 30, 2006

Future of the AVDC/Envisat implementation

• AVDC refinements are being implemented into Envisat Cal/Val

• AVDC/Envisat format being phased into NDACC network» LIDAR, MWR, FTIR completed

• AVDC concept to be extended to NASA A-train (and most probably NPP wrt validation data)

• Format is ESA requirement for ESA/EC GMES program» To be extended to land and radar altimetry

• NASA and ESA to remain synchronized

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November 30, 2006

Closing remarks

• This type of work takes time» Began in 1998, and will be ongoing

• Requires proactive involvement by all parties» Validation teams, instrument PIs, satellite teams, …

• Requires rigid guidelines - down to the measurement level

• Once implemented, it is extremely useful for all involved as experienced for the Envisat and Aura missions when validation relies on very different data sources

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November 30, 2006

bojan.bojkov@gsfc.nasa.gov

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